posted this on electrics and plumbing as not sure where best it suits...

apologies, its a bit long-winded...

i removed an extractor fan from a bathroom ceiling before plastering. there is no ducting - the extracted air just goes up into the space between joists for the ceiling and the floor above (bathroom is on the ground floor). clearly this is not good especially as there are electrics running close by.

to run ducting to the outside is going to be a pain (i can see why they left it, though of course that does not excuse it) i would need to run a duct of around 4 metres or slightly more and go through a double skinned red brick wall. the vent will be in an unsightly place right next to a leaded window on the first floor (pretty chalet bungalow, keen not to spoil the look).

dont really fancy boring a 100m hole if not necessary. there is another route i could take into a roof space for the ground floor extension. the roof space is appx L3m x D2m x H1.5m and is a pitched lean-to roof. so the overall area is around 4.5m³ - the roof space is vented so has a cross flow of air. halogen lights are present in the ceiling below. the roof space is insulated with kingspan. so my question is, can i put the ducting in this space?

is it legal? i suspect i know the answer, and i am sure that there must be a reg stating what can and can't be done. if anybody knows the ruling i'd be grateful to be pointed in the right direction!

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